For years, nutritionists have recommend foods that are high in protein and low in saturated fat. These recommendations often go unheeded by consumers who find a diet of high-fat, sugar-concentrated pastries, candy bars, and soft drinks an irresistible alternative to hard-boiled egg whites, kidney beans, and skim milk. To try and reconcile the sometimes conflicting goals between foods that are healthy and foods that taste good, manufacturers replace some of the less healthy substances in popular foods with healthier ingredients. For example, some of the saturated fats and sugars in conventional ice cream can be replaced with proteins and sugar substitutes that make the ice cream less caloric, and less concentrated in fats and processed sugar. Substituting proteins for fats and carbohydrates has even been extended to foods such as pastas and candy bars.
A significant source of protein used for ingredient substitution comes from the dairy industry, where large quantities of proteins like whey and casein can be separated from dairy milk. Whey protein, for example, is a natural by-product of cheesemaking that has value added uses as a protein substitute. But the native forms of these proteins have physical and organoleptic properties that often make them poor substitutes for fats and carbohydrates. The native proteins also tend to be hygroscopic and soak up the moisture in their vicinity. As a result, solid foods can taste dry, and even liquid drinks can have a chalky aftertaste.
Incorporation of proteins, principally whey proteins, have faced many problems thus preventing their incorporation into food products as the major protein source. For example, whey protein incorporation in to shelf stable beverages is limited due to instability of the protein during heat treatment, resulting in precipitation and/or gelling of the whey protein. Additionally, incorporation of whey protein into nutritional bars leads to bars with shorter shelf life, primarily due to premature hardening of bars compared to bars that have little or no whey protein.
To make dairy proteins a more appealing food substitute, the large native proteins are hydrolyzed into smaller protein fragments (called protein hydrolysates) with protease enzymes. The smaller protein fragments are generally more soluble in water, and less hygroscopic than the starting protein. They can be dissolved in beverages to make concentrated protein drinks, and added to solid foods to impart a smooth, less chalky taste. But cutting the native proteins into fragments also has a significant drawback: Protein hydrolysates are commonly very bitter tasting, and not all protein hydrolysates are heat stable.
The increasing bitterness is attributed to the increased ability of the protein fragments to reach bitter taste receptors on a person's taste buds. Bitterness is tasted when hydrophobic amino acid side groups in the protein fragment can reach these receptors. The large native proteins are so bulky that the bitterness activating side groups have trouble maneuvering to the bitterness receptors, so the native proteins taste bland instead of bitter.
The increased bitterness of protein hydrolysates is predictable enough for food scientists to quantify the relationship between bitterness and protein size by determining the mean hydrophobicity of the hydrolysate, known as its Q-value. The Q-value is calculated by counting the number of amino acid groups (n) that make up the protein hydrolysate, and summing the changes in the free energy for each amino acid group (Δg) as the protein dissolves in the person's mouth. An equation to calculate a protein hydrolysate's Q-value looks like:
  Q  =            ∑              Δ        ⁢                                  ⁢        g              n  
The higher the Q-value the more likely the protein will taste bitter. Because the number of amino acid groups (n) is in the denominator of the Q-value equation, a smaller number of amino acid groups (i.e., a smaller protein) gives a higher Q-value, increasing the chance that the protein will taste bitter. Studies show that most protein hydrolysates with Q-values above 1400 are noticeably bitter, while those with Q-values below 1300 do not taste bitter.
Another procedure to evaluate bitterness in protein hydrolysates is comparing aqueous solutions of the hydrolysates with increasing concentrations of a standard bitter substance such as quinine hydrochloride of caffeine. When the hydrolysates taste equally bitter as a particular concentration of the standard, they are said to have an equivalent bitterness to that concentration level of the standard. Hydrolysate bitterness can be expressed quantitatively as the equivalent to a specific concentration (or concentration range) of a bitter standard solution.
Food and beverage makers have tried several approaches to deal with the bitter taste of protein hydrolysates. These include attempts to mask the bitterness with sweet tasting sugars, and other flavor agents. Flavor agents that cancel the proteins' bitter taste while preserving desired food flavors can be expensive and difficult to develop, and typically do a poor job masking bitter flavors. Use of debittering enzymes during hydrolysis or filtration of the hydrolyzed protein have also been employed to reduce bitterness, although without much success.
In another approach, food makers have tried to cut the protein hydrolysates into smaller peptide units, sometimes even breaking down the protein into individual amino acids. Extensive hydrolysis of proteins down to these sizes has been shown to reduce the bitterness tasted in the larger hydrolysates. But the bitterness is usually replaced with soapy and brothy off-flavors from the peptides that are only slightly more palatable than the bitter tasting hydrolysates. Moreover, bitter flavor and aftertaste are often still noticeable even after the hydrolysis.
Clearly, a large and mostly untapped market can be realized if large native proteins such as dairy milk proteins can be converted into palatable and process stable protein hydrolysates. Not only would such conversion processes create a valuable market for dairy protein by-products like whey, they would also enable consumers to make a seamless transition to healthier foods that are still enjoyable to eat. These processes of making useful, good-tasting protein hydrolysates, as well as various foods and beverages made from them, are described by the present invention.